1. Field of the Invention
The present invention relates to a method of driving an active matrix liquid crystal display device of in-plane switching mode.
2. Related Background Art
Conventional liquid crystal display devices undesirably produce image sticking, in which, when leaving an unchanging image on a screen for a long period of time, a faint remnant of the image remains even after a new image has replaced it. A driving method used to overcome this problem is offset correction to correct the grayscale dependence of voltage drop induced by a gate signal. Another driving method for reducing the image sticking and eliminating flicker in a twisted nematic (TN) liquid crystal display device is as follows. In a grayscale where a source signal has a large amplitude, the voltage of a common signal and the center voltage of the source signal are set to such values as to compensate the voltage drop inducted by a gate signal. In a grayscale where the source signal has a small amplitude, on the other hand, the center voltage of the source signal is set to a value higher than the above center voltage of the source signal for compensating the voltage drop induced by the gate signal. This method is disclosed in Japanese Unexamined Patent Application Publication No. 2001-337310, pp. 2–5, and illustrated in FIG. 8–9, for example.
However, if the driving method described in the above application is applied to a liquid crystal cell of in-plane switching (IPS) mode, it is unable to prevent the image sticking. The liquid crystal cell of the IPS mode has electrodes parallel to each other, which is different from that of the TN mode having electrodes opposite to each other, and a residual DC voltage is more likely to be retained in the IPS mode than in the TN mode, causing the image sticking.